Atomic physics

Scheme that explains the alpha emission.

Atomic physics is the branch of physics that studies the properties and behavior of atoms (electrons and atomic nuclei) as well as matter-matter and light-matter interactions on the scale of individual atoms. The study of atomic physics includes the way in which electrons are arranged around the nucleus and the processes by which this order can be modified, it also includes ions, as well as neutral atoms and any other particles that be considered part of the atoms. Atomic physics includes both classical and quantum treatments, since it can treat your problems from microscopic and macroscopic points of view.

Atomic physics and nuclear physics deal with different issues, the former deals with all parts of the atom, while the latter deals only with the nucleus of the atom, the latter being special due to its complexity. One could say that atomic physics deals with the electromagnetic forces of the atom and converts the nucleus into a point particle, with certain intrinsic properties of mass, charge and spin.

Current research in atomic physics focuses on activities such as the cooling and capture of atoms and ions, which is interesting to eliminate "noise" in the measurements and avoid inaccuracies when performing other experiments or measurements (for example). example, in atomic clocks); increase the precision of the measurements of fundamental physical constants, which helps to validate other theories such as relativity or the standard model; measuring the effects of electronic correlation on atomic structure and dynamics and measuring and understanding the collective behavior of weakly interacting gas atoms (for example, in a Bose-Einstein condensate of few atoms).

Isolated atoms

Atomic physics primarily considers atoms in isolation. Atomic models will consist of a single nucleus that may be surrounded by one or more bonded electrons. It does not deal with the formation of molecules (although much of physics is identical), nor does it examine atoms in the solid state as condensed matter. It deals with processes such as ionization and excitation by photons or collisions with atomic particles.

While modeling atoms in isolation may not seem realistic, if one considers atoms in a gas or plasma, the time scales for atom-atom interactions are enormous compared to the atomic processes that are generally considered. This means that the individual atoms can be treated as if each were isolated, as they are in the vast majority of cases. Through this consideration, atomic physics provides the theory underlying plasma physics and atmospheric physics, although both deal with large numbers of atoms.

Electronic configuration

Electrons form shells around the nucleus. These are normally in a ground state, but can be excited by the absorption of light energy (photons), magnetic fields, or interaction with a colliding particle (typically ions or other electrons).

In the Bohr model, the transition of an electron with n=3 to the n=2 layer is shown, where a photon is issued. A layer electron (n=2) must have been removed previously by ionization.

The electrons that populate a shell are said to be in a bound state. The energy required to remove an electron from its shell (bringing it to infinity) is called binding energy. Any amount of energy absorbed by the electron in excess of this amount is converted to kinetic energy according to the principle of conservation of energy. The atom is said to have undergone the ionization process.

If the electron absorbs an amount of energy less than the binding energy, it will go into an excited state. After a certain time, the electron in an excited state will "jump" (will undergo a transition) to a lower state. In a neutral atom, the system will emit a photon of the difference in energy, since energy is conserved.

If an inner electron has absorbed more than the binding energy (so that the atom becomes ionized), then an outer electron can undergo a transition to fill the inner orbital. In this case, a visible photon or a characteristic X-ray is emitted, or a phenomenon known as the Auger effect can take place, where the released energy is transferred to another bound electron, causing it to enter the continuum. The Auger effect allows multiplying the ionization of an atom with a single photon.

There are fairly strict selection rules for the electronic configurations that can be achieved by excitation by light; however, there are no such rules for collisional excitation processes.

History and developments

One of the first steps toward atomic physics was the recognition that matter was made up of atoms. It is part of the texts written in the VI century BC. C. to II century a. C. like those of Democritus or in the Vaisheshika Sutra or those written by Kanada. This theory was later developed in the modern sense of the basic unit of a chemical element by the British chemist and physicist John Dalton in the 18th century . At this stage it was not clear what atoms were, although they could be described and classified by their (bulk) properties. Mendeleev's invention of the periodic system of elements was another great step forward.

The true beginning of atomic physics is marked by the discovery of spectral lines and attempts to describe the phenomenon, most notably by Joseph von Fraunhofer. The study of these lines led to the Bohr model of the atom and the birth of quantum mechanics. By trying to explain atomic spectra, an entirely new mathematical model of matter was revealed. As far as atoms and their electron shells are concerned, this not only provided a better overview, i.e. the atomic orbital model, but also provided a new theoretical basis for chemistry (quantum chemistry) and spectroscopy.

Since World War II, both theoretical and experimental fields have advanced at a rapid pace. This can be attributed to progress in computer technology, which has enabled larger and more sophisticated models of atomic structure and associated collision processes. Similar technological advances in accelerators, detectors, magnetic field generation, and lasers have greatly aided experimental work.

Notable Atomic Physicists

• Niels Bohr (1885–1962), Danish physicist; Nobel Prize in Physics 1922 (structure of atoms and their radiation), Bohr model of atom, principle of correspondence principle of complementarity
• Steven Chu (born in 1948), American physicist and politician; Nobel Prize in Physics 1997 (atoms that influence lasers, laser cooling), atomic traps and atomic clocks measurements in atomic physics
• Claude Cohen-Tannoudji (born in 1933), French physicist; 1997 Nobel Prize in Physics (cooling and catching atoms with laser light), quantum mechanics, nuclear physics and molecular
• Edward Uhler Condon (1902-1974), American physicist; Franck-Condon Principle atomic energy, radar
• Paul Dirac (1902-1984), British physicist and co-founder of quantum physics, Nobel Prize in Physics 1933 (atomic theory, with Schrödinger); Dirac comb, Fermi-Dirac Statistics, Dirac Sea, Dirac Espinor, Dirac Ecuation, Dirac Function, Dirac Distribution, Dirac Constant, Magnetic Monopothesis
• Enrico Fermi (1901-1954), an Italian-American nuclear physicist; Nobel Prize in Physics 1938, quantum mechanics, quantum statistics, Fermi-Dirac statistics for Fermions gold rule of Fermi, Fermi surface, Fermi resonance model of Thomas-Fermi, first reaction in controlled nuclear chain, atomic bomb, Fermi gas, Fermi level femium, Fermi problems
• Robert Hofstadter (1915-1990), American physicist, Nobel Prize in Physics 1961 for his work on electron dispersal in atomic nuclei determining the size and distribution of load in protons and neutrons.
• Robert Oppenheimer (1904-1967), American theoretical physicist, Scientific Director of the Manhattan Project to develop the atomic bomb
• Ernest Rutherford (1871-1937), British experimental physicist; Nobel Prize in Chemistry 1908 (radioactive disintegration of the elements and chemistry of radioactive substances), discoverer of the atomic nucleus, author of the atomic model of Rutherford, postulate of neutron
• Arnold Sommerfeld (1868-1951), German mathematician and theoretical physicist; Bohr-Sommerfeld atomic model, fine structure constant, Sommerfeld metal theory
• Johannes Diderik van der Waals (1837–1923), Dutch physicist, Nobel Prize in Physics 1910, attraction between atoms, Van der Waals forces, Van der Waals radio, Van der Waals equation